having trouble with encrypted mail - thunderbird, enigmail, gnupg

[Ed Stafford]

I am new to PGP and GNUPG.
Can anyone tell me how to decrypt/read encrypted email messages.
I have two mail addresses that I am experimenting with on seperate
computers.
I have created a key for each address and exported public keys that
were then exchanged, imported and signed.

Then I tried sending signed mail using the recipients pub key...That
worked fine
But if I encrypt it with the recipients pub key, I cannot read or
decrypt it using the recipient email account on the other computer.

I can read signed mail with success, but trying to decrypt encrypted
mail returns an error that there is no secret key available.
I have not found any information on the web to help me.